Strain relief for conductors



Patented Nov. 26 1940 UNITED STATES PATENT OFFICE STRAIN RELIEF FOR CONDUCTORS Daniel M. Seifer, Chicago Heights, 111., assignor to Diamond Wire & Cable 00., Chicago Heights, 111., a corporation of Illinois Application February 10, 1939, Serial No. 255,677

1 Claim. (Cl. 173-322) This invention relates to an improved strain when the wire is fitted through an opening in a relief for conductors such as electric currentpanel or the like.

carrying wires and the like and has, for one of Figure 4 shows a modified form of the invenits principal objects the provision of a simple yet tion and a slightly different method p i- 5 effective means for effectively reducing and cation. 5 practically eliminating any undesirable pull on Figure 5 is a view of a pa e ng various the wire, particularly at the point where the same ope gs t e ein th ou w ich t e Wires with is connected to binding posts or other connections the attached strain relief of this invention may so that there will be no danger of the current be passed.

l connections being-accidentally broken. As shown in the drawing:

One of the important objects of this invention The reference numeral Ill indicates generally is the provision, in a strain relief for an electric the y of the p v ai relief device Of attachment such as a light cord, cable or the t s invention, t e e being Preferably com- 1lk6,'WhlCh will substantially eliminate possibiliposed of flexible vulcanized rubber or similar ties of broken connections at the points where the aterial and having a central longitudinal ope 15' wires are connected to other current-carrying deing the e h for t e pas f a rrent vices such as junction points with radios, electric Carrying electric Cable o t e like ThiS p fans, vacuum cleaners, heating elements, lamp s y be fiy a Cross-Section p k t an ike, cal or may be square or some other shape, de- A still further object of the invention resides pending on the contour of the conductor to which 20 in the incorporation into a wire-of means comthe Strain relief element is pp prising a combined strain relief and reinforcej Outer Sflrface 9f the Strain relief e e e ment which will prevent abrupt bending or break- 1S substammuy in the form of a frustrum of m of the Wire or the insulatiofi at the points of a cone as shown, and when the wire l2 with the most Wear and which furthermore, Wm support attached strain relief element 10 is pulled through 25 any longitudinal pulls which may be imposed upon an opening, the proper Size in a panel H the wire during operation of the attached device, shown in figure h strain relief elgment. W111 while, at the same time, facilitating the assembly finally come to a point where its outside diam of the wire into any particular electrical unit. liter i than the mside dmmeter of the open A further object of the invention is the promg m the panel 9 other element 30 vision of a strain relief for wires which can acwhereupon the resilient mammal of the stmm tually form a, part f th insulation and which 6118; element ill will become compressed upon will readily adapt itself to openings in the pang g: :5 gi i ggg gg gzg i fi z ga els or housings of instruments regardless of the Shape of the p g and which, furthermore, can nor backward owing to the tendency of the rubher or h lik be employed from either direct1on especially so trated i g g g expand and bulge as is mus far asdapplication to some electrical device is con- If it is desired to insert a conductor 5 w a cel'ne strain relief element i8 thereon through an open- 40 Other and further impo t nt obi of ing in apanel or plate 20 from the outside there- 40 invention will be appare from the disclosures of and still maintain a strain relief relationship in the accompany wi a following p with the free ends of the exposed wires 22, a iflcation. slightly different form of the device of this in- The invention, in Dreferfed form, 15 Shown vention is provided as illustratedin Figure 4, the

in the d aw and hereinafter more fully difierence being that the resultant outer end 45 scribed. 24 is rounded as shown rather than squared as In the drawing: is the case with the element of Figure 3. This Figure l is a side view of the improved strain rounded effect provides a more neat appearing relief element of this invention, the same being result on the outside of the cabinet of hi h r0 shown in section and as considerably enlarged. the plate or panel 20 may form a part, and it Figure 2 illustrates the device in position on has been found by experience and tests that a flexible electric current carrying cable or the if the conductor [6 is pulled through the openlike. ing to such an extent that a firm wedging oc- Figure 3 is a sectional view showing the elecurs, it; will be practically impossible to remove ment in actual operating relationship on a wire the same with the attached strain relief with-' 55 opening such as shown at may be used, and

even an oval or elliptical opening 32 can be employed with considerable advantage in some instances.

If a more positive gripping effect is desired, the inner face of the opening may be provided with gripping teeth or the like as illustrated at 34 in the rectangular opening or at 30 in the circular opening shown.

The strain relief device of this invention may be applied to the conductors l2 and I 8 by vulcanizing the same in position or by actually molding the same at the time that the conductors are made, or, if desired, the strain relief element can be applied to a conductor by simply slipping the same thereover to a desired point and then cementing it in position by means of a suitable adhesive.

It will be evident that herein is provided an improved reinforcement and strain relief for a current-carrying cord which may be economically manufactured and which, furthermore, may be simply installed with a minimum expenditure of time and labor, and which, when installed, provides ample resistance to damage to the cord or nections are concerned. Use of such a strain relief also eliminates possibility of shorting which results from tying knots in the cord or the use of metallic clamps which sometimes cut through the insulation.

I am aware that many changes may be made and numerous detailsjof construction varied throughout a wide range without departing from the principles of this invention, and I, therefore, do not purpose limiting the patent granted hereon otherwise than as necessitated by the prior art.

I claim as my invention:

In combination, an insulation coated electrical conductor with strain relief, a comparatively thin plate having an aperture through which the conductor is passed, the strain relief comprising a smoothly molded frusto-conical enlargement of v the conductor coating, the said enlargement composed of resilient material, the smallest diameter of the enlargement being slightly less and the largest diameter of the enlargement being slightly its terminals, particularly so far as broken congreater than the diameter of the cylindrical aperture into which the conductor with its attached strain relief is fitted so tightly that a circumferential bulge rises adjacent the small diameterside of the frusto-conical enlargement-preventing extraction.

DANIEL M. SEIFER. 

